The present invention relates to a color gamut displaying method, an image processing method, and an apparatus capable of utilizing the methods, which are suitable for a color management system, and the like, for instance, reproducing colors faithfully in consideration with characteristics of a color input/output device.
As shown in FIG. 32, color ranges which can be reproduced by devices, such as a scanner, a monitor, and a printer, are different each other.
In FIG. 32, x and y denotes axes for chromaticity, and insides of closed areas are color gamuts.
In other words, the key to reproduce colors after considering the difference in a color gamut is how to deal with portions of ranges which are not common to different devices. For example, when transformation from a monitor color space to a printer color space is considered, a major problem is that which color should be used to express a color outside of a color gamut of a printer. A process to deal with the above-said problem is called a color gamut compression process.
A color management system has major functions, such as a function of performing the color gamut compression process for faithfully reproducing colors in consideration with characteristics of a color input/output device, as well as a color gamut checking function for checking whether or not it is possible to reproduce a color by an output device. The latter function is used to determine whether or not color data, included in an application software and the like, can be reproduced by an output device (e.g., printer monitor).
Specifically, a method which is shown in FIG. 34 is suggested by the present inventor.
According to the method, a color gamut of a printer is defined by a color reproduction solid whose shape is a hexahedron, determined by peaks of red, green, blue, cyan, magenta, yellow, white, and black. Then each surface of the hexahedron is divided into two triangles to obtain total of twelve areas. Finally, image data is determined whether it is inside or outside of the areas, thereby it is determined if the image data is in the color gamut or not.
However, there are problems to be solved in the aforesaid method.
(1) A real color gamut of a printer has a three dimensional solid which is too complicated to express with a hexahedron, thus precision of checking the color gamut is low.
(2) It is not a simple process to determine whether or not image data is inside of the twelve areas, thus it requires a long time to complete the process.